Vertical lines on the palm anywhere is a good indication. On the phalanges too it is a good indication. Better read the book "The Laws of Scientific Hand Reading" where William G. Benham has given detailed reading about the phalanges.

vertical lines on phalanges show you are trying to 'break through' any problems, making positive efforts, active use of energy, projecting yourself out into the world. But too many vertical lines can show too much activity / striving & stress (trying too hard, burning yourself out).

I first read about it in William G. Benham's book but he has just asked you to reason it out just like you did. In some other books I have just read about certain indications on certain phalange means so and so but there is no detailed discussion of these lines on all phalanges. I remember one palmist in an Astrological Magazine wrote one horizontal influence line on the middle phalange of the Jupitor Finger means Diplomatic. Vertical line on this phalange would mean ambitious so the horizontal one Diplomatic.